Random access slide stainer with independent slide heating regulation

ABSTRACT

An automated slide stainer with slides mounted in a horizontal position on a rotary carousel. Reagents and rinse liquids are automatically dispensed onto tissue sections or cells mounted on slides for the purpose of performing chemical or immunohistochemical stains. The rinse liquids are removed by an aspiration head connected to a source of vacuum. Individual slides or groups of slides are supported on flat heating stations for heating to individual temperatures. Temperature control electronics on the carousel are controlled by a user interface off of the carousel.

RELATED APPLICATION(S)

This application is a continuation of U.S. application Ser. No.10/864,620, filed Jun. 9, 2004, now U.S. Pat No. 7,217,392, which is adivisional of U.S. application Ser. No. 10/027,746, filed Dec. 20, 2001,now U.S. Pat. No. 6,783,733, which is a continuation of U.S. applicationSer. No. 09/688,619, filed Oct. 16, 2000, now U.S. Pat. No. 6,541,261,which is a divisional of U.S. application Ser. No. 09/032,676, filedFeb. 27, 1998, now U.S. Pat. No. 6,183,693. The entire teachings of theabove applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Tissue sections or cellular monolayers are commonly examined bymicroscopic examination, for both research and clinical diagnosticpurposes. Thin tissue sections or cellular preparations are commonly1-10 microns thick, and are nearly transparent if untreated. In order tovisualize various histologic features, a wide array of stainingprocedures have been developed over the years that highlight variouscellular or extracellular components of the tissues. Histochemicalstains, also commonly termed “special stains,” employ chemical reactionsto color various chemical moieties. Immunohistochemical stains employantibodies as probes to color specific proteins, commonly via enzymaticdeposition of a colored precipitate. Each of these histochemical andimmunohistochemical stains requires the addition and removal of reagentsin a defined sequence for specific time periods, at definedtemperatures. Therefore, a need arises for a slide stainer that canperform a diversity of stains simultaneously under computer control, asspecified by the technologist.

An early slide stainer for immunohistochemistry was described by DavidBrigati M.D., U.S. Pat. No. 4,731,335. In that disclosure, microscopeslides were closely apposed to each other, to form capillary gaps. Thepairs of slides were mounted in a holder that could be moved about by amechanical arm along three axes. If slides were to be heated, all of theslides were moved as a group into a humidified heated chamber.Therefore, random access capability is not possible with this design.

In another slide stainer by Rogers and Sullivan, U.S. Pat. No.4,043,292, slides are mounted on a rotary carousel. Their inventionheats the slides by passing a heated stream of air over the slides. Allof the slides are heated to the same temperature.

Wooton, McLeod, and Read disclose another slide stainer thatincorporates heat capability, in U.S. Pat. No. 5,231,029. In thatinvention, a steam chamber is provided to heat slides. The humidity inthe steam chamber is designed to be just below 100 percent. If theslides are to be heated, they are placed into the chamber. Since theslides are either in or out of the chamber, all slides must be broughtto the same heated temperature, a temperature approximately that ofsteam (100° C.).

A recently described batch slide stainer commercialized by VentanaMedical Systems, Inc. is disclosed in U.S. Pat. No. 5,595,707 byCopeland, et. al. In that disclosure, slides are placed on a rotarycarousel that allows for the addition and flushing of reagents from theslide surface. Their slide stainer includes a heating chamber that isheated by the introduction of warm air. A temperature sensor iscontained within the chamber for providing temperature feedback to amicroprocessor. Similar to the other slide stainers described above, allslides must be brought to the same temperature.

SUMMARY OF THE INVENTION

This invention relates to an improved slide staining device, for theapplication and removal of reagents to biologic tissue sections mountedon microscope slides. The improvement relates to the random accesscapability of the slide stainer, i.e., one that performs any of a listof procedures to any of a plurality of biologic samples mounted onmicroscope slides. Since various procedures require heat at differenttimes to enhance the rate of chemical reaction, a means has beendeveloped to heat slides to different temperatures, independently of thetemperatures of other slides. This invention allows for heating eachslide to its own specified temperature.

Any of the previously-described systems could potentially be modified toduplicate their heater control systems to provide for multiple levels ofheating control. For example, commercial thermal cyclers are nowavailable that incorporate four different heating blocks that share thesame microprocessor. However, the type of hard-wired temperature controlmechanism that heats and cools four different blocks would be expensiveand cumbersome as the number of independent samples increases. Forexample, in the preferred embodiment of the present invention,forty-nine independent heating positions are described. If we assumethat two wires provide power to the heater, and two wires providetemperature feedback from each heating sensor, then a total of 196 wireswould need to be connected between the different heaters and thecomputer control circuitry. Placing all of these wires on a service loopbetween a stationary computer and a moving slide stainer presents yetanother difficulty, increasing the cost of manufacture and servicing.

In accordance with one aspect of the invention, a moving plating,preferably a carousel, is adapted to support a plurality of microscopeslides bearing biological samples. In particular, a plurality of flatheating stations are provided on the platform, each heating stationsupporting at least one microscope slide and, in a preferred embodiment,each heating surface supporting a single microscope slide. The heatingstations are individually controlled to control temperatures to whichthe slides are heated.

According to another aspect of the invention, a plurality of heatersthat can each heat at least one slide are associated with a movingplatform that is adapted to support a plurality of microscope slides.Each heater includes a heating element set, each set having at least oneheating element. A temperature controller electronic circuit mounted onthe moving platform provides electrical power to the heating elementsuch that each heating element set can be heated to a differenttemperature. A user interface mounted off of the moving platformspecifies the desired temperatures for the microscope slides through acommunication link with the temperature controller electronic circuit.

Preferably, the communication link is a group of wires, the number ofwires being fewer than the number of heating elements. To that end, thetemperature controller electronic circuit may include a shift registerwhich receives control data from the user interface, multiple shiftregisters of plural controllers being daisy chained. Individualtemperature sensors may also be provided to provide temperature feedbackinformation to the temperature controller electronic circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1 is a perspective view of a first embodiment of a slide stainer.

FIG. 2 is a top view of a slide frame for providing five sealed cavitiesabove five different slides holding tissue samples.

FIG. 3 is a top view of a slide frame base.

FIG. 4 is a bottom view of a slide frame housing.

FIG. 5 is a top view of the slide frame housing with five microscopeslides in their appropriate positions, showing the area to which heat isapplied.

FIG. 6 is a cross-sectional view of a slide frame resting on the sliderotor.

FIG. 7 is a schematic diagram of the heater and sensor wiring diagram,on the slide frame, and the interconnection with the temperaturecontroller.

FIG. 8 is a side cross-sectional view of a cartridge pump dispensingmechanism in the liquid dispensing and removal station.

FIG. 9 is a side cross-sectional view of a bulk liquid dispensingstation housed in the liquid dispensing and removal station.

FIGS. 10A and 10B are side cross sectional views of a vacuum hose andtransport mechanism for removing liquid reagent and wash fluids fromslides contained on the slide rotor.

FIG. 11A is a side cross-sectional view of the aspiration head, showingits relationship to the glass slide in the slide frame.

FIG. 11B is a bottom en face view of the aspiration head.

FIG. 12 is a perspective view of a second embodiment of a slide stainer.

FIG. 13 is a perspective view of the liquid handling zone of the secondembodiment of the slide stainer.

FIGS. 14A and 14B are side cross-sectional views of the liquidaspiration station of the second embodiment, with the aspiration head inthe lowered (FIG. 14A) and raised (FIG. 14B) positions.

FIG. 15 is a schematic representation of the waste liquid pathways ofthe second embodiment.

FIG. 16 is a schematic representation of the bulk liquid dispensepathways of the second embodiment.

FIG. 17 is a schematic representation of the individual heaters on theslide rotor and the temperature control boards mounted on the sliderotor.

FIGS. 18A-D are a schematic diagram of the electronic circuitry of thetemperature control board.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a first embodiment 1 of the invention in perspective view.Generally, the first embodiment 1 comprises a substantially circularassembly base 2, a slide rotor 3 rotatable on the assembly base 2, areagent rotor 4 also rotatable on the assembly base, and a liquiddispensing and removal station 5.

The slide rotor 3 is driven to rotate by a servo motor (not shown) andcarries ten slide frames 6 that are radially asserted into anddetachable from it. A top view of single slide frame 6 is shown in FIG.2. Here, positions for five slides, each with a tissue sample, are shownin positions 7 a-7 e. The slide frame 6 comprises a slide frame base 8shown in FIG. 3. The slide frame base 8 includes a heated area 9 whichunderlies each of the slide positions 7 a-7 e and incorporates resistiveheating elements, not shown. The heating elements are integrally formedin the slide frame base 8. Electricity for powering the heating elementsis provided into the slide frame 6 from the assembly base 2 via firstand second contacts 10. Further, third and fourth contacts 11 enabletemperature sensing of the heated areas via thermocouples alsointegrally formed in the slide frame base 8. In practice, a sum of threeconnectors are required, since contacts 10 and 11 share the same groundconnection. Therefore, one of the connectors 11 are left unused.

Adapted to overlay the slide frame base is a slide frame housing 12.FIG. 4 is a top view of the slide frame housing 12 showing essentially arigid plastic or metal frame 13 with five oval holes 14 a-14 ecorresponding to each of the slide positions 7 a-7 e. A silicon rubbergasket 15 is also provided under the frame 13. Returning to FIG. 2, theslide frame housing 12, including the gasket 15 and frame 13, is boltedonto the slide frame base 8 by two Allen bolts 16 to provide individualsealed cavities approximately 0.2-0.4 inches deep over each tissuesample slide placed at each of the slide positions 7 a-7 e. As a result,a total of 3 ml of reagents and/or rinses can be placed in contact withthe tissue samples of each one of the slides but a maximum quantity of 2ml is preferable. Since the silicon gasket 15 is compressed by the frame13 against the microscope slides (not shown), the cavities over each ofthe frame positions are mutually sealed from each other.

FIG. 5 is a top view of a slide frame base 8 with five microscope slides17 in the positions denoted by 7 a-7 e in FIG. 3. The area of each slide17 forming cavities, that are delimited by the silicone rubber gasket 15and holes 14 a-14 e is indicated by an approximately rectangular line18, marking the chamber wall. The area denoted by the hatched barsindicates the area of the slide frame base 8 that includes heatingelements 9. The entire heated area (hatched bars) is raised to the sametemperature, bringing the group of five slides to the same desiredtemperature. The portion of each slide 17 that is not above the heatedarea does not generally bear a biologic tissue specimen. Rather, it isused for labeling purposes.

FIG. 6 is a cross-sectional view of an assembled slide frame base 8 andhousing 12, collectively referred to previously as the slide frame 6.The microscope slide 17 is shown held in position, between the slideframe base 8 and housing 12. The slide frame 6 is resting on the sliderotor 3. In this view, the electrical connection between the slide frame6 and an edge connector 19 is demonstrated. Four edge connectors perslide frame 6 are provided (contacts 10 and 11 in FIGS. 2 and 3). Theelectrical connection is fed from the edge connector 19 through theslide rotor via an insulated feed-through 20, to a terminal underneaththe slide rotor 3. A wire then connects the terminal to a source ofpower or control circuitry (not shown).

FIG. 7 is a schematic diagram, showing two out of the ten heater 91 andsensor 92 circuits that can be placed on the instrument slide rotor. Theheater is represented schematically as a resistive element, andcorresponds to the heated area (hatched bars) of FIG. 5. Contacts 10 and11 share a common ground connection, leaving one of the four connectorsunused. Each of the circuits feeds into a temperature controller,represented schematically 21. Each slide frame sends three wires to thetemperature controller 21—a heater power conductor 22, a sensorconductor 23, and a ground connection 24. The temperature controller 21is mounted in a stationary position on the assembly base 2. Since theheaters and sensors are in frequent motion, they connect to thestationary temperature controller 21 via a service loop (not shown). Theservice loop contains the wires from each of the edge connectors 19.Sufficient extra length is provided in the wires so that as the sliderotor rotates, the service loop travels around the slide rotor axis. Theslide rotor 3 does not turn more than one full revolution in eitherdirection. The wires in the service loop are preferably bundled togetherwith a wire tie, so that individual wires do not become entangled orcaught underneath the slide rotor 3. Since there are three wires percircuit (wires 22-24), and there are ten slide frames 6 on the sliderotor 3, the service loop contains a minimum of thirty wires.

Referring to FIG. 1, positioned above the slide rotor 3 is the reagentrotor 4. This reagent rotor is similarly adapted to rotate on theassembly base 2 and is driven by another servo motor (not shown) undercomputer control (not shown). The reagent rotor 4 and the slide rotor 3rotate independently of each other. The reagent rotor 4 is adapted tocarry up to ten cartridge frames 25. Each of these cartridge frames 25are detachable from the reagent rotor 4 and can be selectively attachedat any one of ten possible points of connection. Each cartridge frame 25is capable of carrying five of the cartridge pumps 46.

Generally, the dispensing station 5 comprises a soft hammer 26 forengaging a portion of the cartridge pumps 46. The cartridge pumps 46 areconstructed so as to dispense liquid when a portion of the cartridgepump 46, called the metering chamber 42 of the cartridge pump 46 iscompressed. It is possible to dispense from any of a plurality ofcartridge pumps by rotating the reagent rotor so as to align a desiredcartridge pump 46 with the hammer 26. This provides the capability ofdispensing precisely measured amounts of reagent to any slide positionedunderneath the cartridge pump 46 adjacent to actuator 26. The mechanismfor dispensing from the cartridge pumps 46 is shown in greater detail inFIG. 8. The hammer 26 is driven by a solenoid or linear stepping motor43 that is mounted on a front wall 44, attached to the assembly base 2.In FIG. 8, the hammer is shown compressing the metering chamber 42portion of the cartridge pump. It is important to be able to adjust thespeed of compression by the hammer 26 upon the metering chamber 42.Otherwise, too rapid a compression will cause an excessively forcefulejection of reagent from metering chamber 42, potentially damaging thetissue section underneath. Therefore, a linear stepping motor ispreferred instead of a solenoid. As another alternative, thereciprocating hammer of the dispensing actuator could take the form of acam, driven by a rotary motor, that engages the metering chamber 42 sothat the rotation of the cam will compress the metering chamber.

The cartridge pump 46 is comprised of a liquid reservoir 45 and themetering chamber 42. The liquid reservoir 45 shown in this firstembodiment 1 is a syringe barrel. The metering chamber 42 is comprisedof a compressible elastomeric housing with a one-way inlet valve (notshown) and a one-way outlet valve (not shown), both valves aligned in adownwards direction of fluid flow. When the hammer 26 compresses themetering chamber 42, the liquid reagent contained within is ejected.When the compressive force is removed, the negative pressure created bythe expansion of the elastomeric housing, trying to resume its native,non-compressed shape, causes liquid to flow inwards from the liquidreservoir 45. In this manner, repetitive compression of the meteringchamber 42 causes repetitive dispensing of small aliquots of reagent.Alternative cartridge pumps are presented in U.S. patent applicationSer. No. 08/887,178 filed Jul. 2, 1997 and U.S. patent application Ser.No. 09/020,983 filed Feb. 10, 1998 which are incorporated herein byreference.

The dispensing station 5 further includes a means to dispense liquidsfrom a large bottle (FIG. 9). Bulk liquid bottles 27 that can supplyliquid into any one of the microscope slides 17 on any one of the slideframes 6 via rinse tubes 28. Each bulk liquid bottle 27 is connected toits own rinse tube 28. The bulk liquid bottles 27 are pressurized by apump (not shown). The outflow tube (not shown) from each bulk liquidbottle 27 passes through a valve 47 that regulates the flow of liquidfrom that bottle. By opening the valve for a defined period of time,under computer control (not shown), with a defined pressure within thebottle 27, a known quantity of liquid can be dispensed onto the slide17. The liquids placed within the bottles 27 are those that are usedrepeatedly among many different procedures, such as water, saline, andalcohol.

As shown in FIG. 9, the bulk liquid bottles 27 are screwed into a femalethreaded cap 48 secured to the underside of the horizontal top wall 49of the station frame. Compressed air from a compressor (not shown) isprovided to each bulk liquid bottle 27 through a pressure regulator 50.Tubing from the pressure regulator 51 transmits the compressed air tothe inlet of the bulk liquid bottle 27. The pressure above the liquidenables the liquid to forced up through the dip tube 52 through therinse hose 53 when a pinch valve 47 is opened. Depending on the lengthof time that the pinch valve is opened, a pre-determined amount ofliquid can be dispensed through the rinse tube 28.

The liquid dispensing and removal assembly 5 further includes a liquidremoval vacuum station, positioned adjacent to the rinse tubes 28 (notvisible in FIG. 1). In order to remove liquid from the surface of aslide 17, the reagent rotor positions the slide at the liquid removalvacuum station, shown in a side cross-sectional representation in FIGS.10A and 10B. An external source of vacuum (not shown) is channeledthrough a trap flask 29, ultimately leading to a vacuum hose 30 thatterminates in an aspiration head 31. The tubing connections are notshown in FIGS. 10A and 10B. The vacuum hose 30 and aspiration head 31are supported by a hose transport mechanism 54 that allows theaspiration head 31 to be extended down into a cavity of a slide frame 6to remove liquid covering the tissue sample on the slide 17. As theaspiration head contacts the liquid, the liquid is sucked upwards intothe tubing and collected into the trap flask 29.

The vacuum hose transport mechanism 54 comprises a motor 32. Areciprocating link 33 is attached to a crank arm 34 so that the rotationof the motor 32 causes the reciprocating link 33 to traverse in avertical direction. A bottom portion of the reciprocating link 33 isconnected to a lever 55 that is pivotally attached to the station frame.The other end of this lever is connected to a vacuum hose clamp 35 thatis connected via pivot arms 36 to a plate 37 rigidly attached to thestation frame. The net effect of these connections is that when themotor 32 is rotated, the slide arm 33 descends in a vertical direction.Thus, the lever 55 is pivoted clockwise around its fulcrum causing thehose clamp 35 to pivot up and away on the two pivot arms 36 from theslide as shown in FIG. 10B. The motor is automatically turned off as thelink 33 reaches its two extreme ends of movement by the contact of theelectrical terminals 39 of the link to the contact plates 38 connectedto the station frame.

The aspiration head 31 is shown in greater detail in FIGS. 11A and 11B.FIG. 11A shows the aspiration head in a lowered position, incross-section, within the cavity formed by the slide frame 6. Theaspiration head 31 comprises a hollow interior manifold 40 through whichthe vacuum force is transmitted across the entire lower surface of theaspiration head 31. Eight holes 41 are drilled on the lower face of theaspiration head 31, through which the suction force is transmitted.Since the microscope slide 17 is planar, liquid on the slide surfacespreads out in two dimensions. Therefore, in order to thoroughly removeliquid from all portions of the microscope slide 17, multiple aspirationsites are needed. We accomplish this with an aspiration head with aplanar lower surface with multiple holes. The planar surface of theaspiration head 31 comes into close parallel apposition to themicroscope slide 17. The aspiration head only contacts the liquid, notthe microscope slide itself, lest it damage the glass slide 17 or thebiologic specimen that it carries (not shown). Without such a design andonly a single aspiration site, such as from a pipette, liquid distantfrom the aspirator would not be removed. Rather, it would cling to thedistant surfaces of the glass slide 17, because of the surface tensionon the glass. This would result in a residual volume of liquid thatwould otherwise be left on the surface of the slide 17. Having a closeparallel apposition of the aspiration head is also helpful from theperspective of decreasing surface tension during liquid aspiration. Theclose parallel apposition of the bottom surface of the aspiration headwith the microscope slide 17 creates a type of capillary gap. This gaphelps to overcome surface tension, ensuring complete liquid removal.

A computer, not shown, controls the instrument functions. That is, anoperator programs the computer with the information such as the locationof reagents on the reagent rotor and the location of slides on the sliderotor. The operator then programs the particular histochemical protocolto be performed on the tissue samples. Variables in these protocols caninclude the particular reagent used on the tissue sample, the time thatthe tissue sample is allowed to react with the reagent, whether thetissue sample is then heated, the rinse that is then used to wash thereagent away, followed by the subsequent removal of the rinse andreagent to allow subsequent exposure to a possibly different reagent.The instrument enables complete random access, i.e., any reagent to anyslide in any sequence.

A second, preferred, embodiment of the invention is shown in FIG. 12.Like the previous embodiment, it also comprises two independentcarousels that rotate on an assembly base 56. Bulk liquid bottles 57 aremounted on a bridge 58 that extends across the width of the entiremachine, above the reagent rotor. A separate group of trap bottles 59,for collecting waste liquid, are mounted on the side of the bridge 58 ina compartmentalized shelf. The tubing connections and valves for thebulk liquid bottles 57 and the trap bottles 59 are hidden from view byan upper panel 60. The front and sides of this embodiment are surroundedby a plexiglass case 61, that can be manually slid sideways in order toinsert cartridge pumps 62 or slides (not shown). Slides are individuallyinserted and removed via a centrally located slide access door 63. Theslides (not shown) are hidden from view by a circular platen 64 that islocated above the slides and reagent rotor (not shown). Functionssimilar to the dispensing assembly (5 of FIG. 1) in the previousembodiment are accomplished in a somewhat similar liquid handlingassembly (not shown) that is positioned in a liquid handling zone 65.

FIG. 13 shows the individual mechanisms contained within the liquidhandling zone 65, including a hammer 66 for dispensing from cartridgepumps (not shown), an aspiration head 67 for removing liquid from thesurface of slides, a bulk liquid dispensing port 68, and an air-mix head69 for spreading and mixing liquids on the surface of a slide. Theelectromechanical mechanism for dispensing from cartridge pumps, bycompressing a hammer 66 upon a metering chamber of a cartridge pump (notshown in FIG. 13), is similar to the previous embodiment (FIG. 8).Reagent dispensed from the cartridge pump (not shown) flows onto theslide by passing through a roughly rectangular hole in the platen 64.

The aspiration head 67 also functions in a similar manner to that of theprevious embodiment. In order to simplify the linkage mechanism forlowering and raising the head 67, the head moves solely in a verticaldirection. This is shown in further detail in FIGS. 14A and 14B. FIG.14A shows a side cross-sectional view of the aspiration head in a downposition, within a cavity formed by the microscope slide 75 (bottomsurface) and a slide chamber clip 76 (lateral walls). As in the firstembodiment, a gasket (not shown) seals the surface where the slidechamber clip 76 contacts the microscope slide 75. A linear stepper motor73 moves the aspiration head up and down, under computer control(demonstrated schematically in FIG. 15). As in the first embodiment 1,the aspiration head 67 comprises a hollow manifold 74 connected to asource of vacuum. Eight holes communicate between the bottom of theaspiration head 67 and the exterior, through which liquid is aspirated.When vacuum is supplied to the aspiration head 67, and the head 67 islowered adjacent to the slide, the liquid reagent on top of the slide isaspirated off and collected in a trap bottle 59 (shown schematically inFIG. 15). When the aspiration head 67 is not in use, it is raised to theup position (FIG. 14B), allowing free rotation of the slide rotor 77.

FIGS. 14A and 14B also show the physical location of a heating element78, represented as a resistive element inside a rectangular box withcross-hatched lines. Each slide rests directly on the heating element78, so that heat is directly communicated to the microscope slide. Athermistor is incorporated into each heating element (not shown in FIGS.14A and 14B). Each of forty-nine microscope slides 75 has its ownheating element 78, so that the temperature of each slide 75 can beindependently regulated. Power for the heating element 78 is supplieddirectly from a temperature control board 79 that is affixed to theunderside of the slide rotor 77. Seven identical temperature controlboards 79 are so mounted underneath the slide rotor 77, evenly spacedaround the periphery. Each temperature control board supplies power forseven heating elements 78. The means by which this is accomplished isexplained later, in reference to FIGS. 17 and 18A-D.

An important aspect of this embodiment, not highlighted in the previousembodiment 1, is the provision for the segregation of waste liquids thatare removed from the surface of the slide. A schematic diagramexplaining how this is accomplished is shown in FIG. 15. Three differentwaste bottles 59 are mounted on the instrument. Connections 70 are alsoprovided on the instrument for a large external trap bottle 71,typically of a ten or twenty liter capacity for aqueous waste. Foursolenoid valves, labelled 80A-80D control to which bottle aspiratedliquid will be directed. These valves are under computer control,schematically represented by the box labelled “controller” 86. Valve 81is a three way valve. It can allow a direct connection between thevacuum pump 82 and the overflow trap 83, or between the pump and theambient environment. A connection to the ambient environment is requiredif the aspiration system needs to be bypassed when the air-mix head 69is in use. If valves 80A and 81 are appropriately opened, the pump 82turned on, and the aspirator head 67 lowered so as to aspirate liquid,the liquid will be directed upwards into the tubing, as represented bythe arrow “fluid flow.” Liquid will then follow the only path available,and be collected into the external trap bottle 71. Valves 80B-80Dfunction similarly for their respective trap bottles 59. A smalloverflow trap bottle 83 is also inserted into the line with its ownfluid sensor 93. This provision is included so as to detect if any ofthe trap bottles 59, or external trap bottle 71 are overflowing withwaste liquid. In that case, liquid would enter the overflow trap bottleand be detected by the fluid sensor. That information would becommunicated to the controller 86, which would shut the system down andalert the instrument operator on the computer screen.

Referring to FIG. 13, the liquid handling zone also includes an air-mixhead 69. A schematic representation of the air flow into the air-mixhead 69 is shown in FIG. 15. The pump generates a high velocity airstream that is channeled into the air-mix head 69. Air intake to thepump is via the three way solenoid valve 81 (FIG. 15). The solenoidvalve 81 (FIG. 15) switches so as to channel air directly from theatmosphere to the pump (FIG. 15), bypassing the aspiration system andtrap bottles 59 and 71. The high velocity air flow is focused onto theslide. The air-mix head 69 travels back and forth along the length ofthe slide, pushed and pulled by a belt and pulley that is attached to amotor (not shown). The net effect of this system is to direct a curtainof air back and forth along the length of the slide, causing liquid tobe mixed and spread along the surface of the microscope slide.

The liquid handling zone 65 (FIG. 12) includes a bulk liquid dispensingport 68 (FIG. 13). The function of the rinse tubes 28 of the firstembodiment 1 (shown in FIG. 1) are all incorporated into a single bulkliquid dispensing port 68 in this preferred embodiment. Therefore,slides are positioned under the bulk liquid dispensing port 68regardless of the bulk liquid bottle that the liquid is actually derivedfrom. A schematic representation of the fluid pathways and controlvalves is shown in FIG. 16. The bulk liquid bottles 57 are eachconnected to a source of pressure, that is generated by a pump 85. Thepressure is communicated to the bulk liquid bottles 57 via a pressuremanifold 94. Solenoid valves 72 a-72 f are placed between the bulkliquid dispensing port 68 and each bulk liquid bottle 57. Liquid flowsout the bulk liquid dispensing port 68 only when one or more of thevalves 72 a-72 f are open. A pressure switch 84 also communicates withthe pressure manifold 94. It is capable of sensing the amount orpressure contained within the manifold 94. When it falls below aspecified level, it communicates with the controller 86 causingactivation of the pump 85. As the pump generates an increased amount ofair pressure within the pressure manifold, the pressure switch resets,causing the pump to stop pumping. In this manner, a relatively constantpressure head is maintained within the pressure manifold 94.

A dispense sensor 95 is positioned underneath the bulk liquid dispensingport 68 to provide verification that liquid was dispensed when one ofthe solenoid valves 72 a-72 f were transiently opened. The dispensesensor 95 comprises an optical sensor and an LED light source. Whenliquid is dispensed from the bulk liquid dispensing port 68, the liquidinterrupts the light beam. The change in resistance across the sensor asa result of the decrement in light intensity is communicated to thecontroller 86.

This second, preferred embodiment of the invention includes thecapability to independently heat the forty-nine slides to differenttemperatures. A novel aspect of this embodiment is the method forindependently regulating the amount of power that each of the forty-nineheaters receives. Moreover, each heater also incorporates a temperaturesensor. Each of these sensors must communicate with the computer 86 inorder to allow for appropriate temperature feedback and regulation. Inthe first embodiment 1, groups of up to five slides were under a single,common temperature control mechanism. Each heating group had wires thatdirectly connected with the temperature controller (FIG. 7). With threewires per group (power for heat, sensor feedback, and a shared ground)and ten groups of slides, at least thirty wires were contained in theservice loop. If a similar system were used for forty-nine differentheaters, as in this preferred embodiment, 147 wires would be required inthe service loop. Such a bulky service loop would be problematic.Therefore, an alternative method is developed in this preferredembodiment.

FIG. 17 shows the relationship between each of the heating elements 78mounted on the slide rotor 77, depicting the heating element 78 as aresistive element. A single sensor 87 is adjacent to each heater. Thecombination of a single heating element 78 and sensor 87 are sopositioned so as to provide a location 88 for a single slide to beheated. The physical layout of this location 88 is demonstrated in FIGS.14A and 14B. Two wire leads from each heating element 78, and two wireleads from each sensor 87 are connected directly to a temperaturecontrol board mounted on the slide rotor 77. Each temperature controlboard is capable of connecting to up to eight different heater andsensor pairs. Since this embodiment incorporates forty-nine slidepositions, seven boards 79 are mounted to the underside of the sliderotor, each connecting to seven heater-sensor pairs. One heater-sensorposition per temperature controller board 79 is not used. Also shown inFIG. 17 is the serial connection 89 of each of the seven temperaturecontrol boards, in a daisy-chain configuration, by six wires. The firsttemperature control board is connected via a service loop 90 to thecomputer 86. The service loop contains only six wires tied together in aharness.

FIGS. 18A-D are an electronic schematic diagram of the temperaturecontrol board 79. The design of the temperature control board 79 wasdriven by the need to minimize the number of wires in the flexible cable(service loop 90) between the heaters and the computer. To minimize thelength of wires, seven temperature controller boards 79 are used, eachmounted on the slide rotor. Thus, each heater is positioned close to itsassociated electronics and the size of each board 79 is kept smallbecause each runs only seven heating elements 78. Each temperaturecontroller board 79 includes the function of an encoder and decoder oftemperature data. That data relates to the actual and desiredtemperature of each of heating elements 78. The data flows back andforth between the computer 86 and the temperature control board 79. Ifan individual heating element 79 requires more or less heat, thecomputer communicates that information to the temperature control board79. The temperature control board 79, in turn, directly regulates theamount of power flowing to each heater. By placing some of the logiccircuitry on the slide rotor, in the form of the temperature controlboards 79, the number of wires in the service loop 90, and their length,are minimized.

In this embodiment, the temperature control board 79 system was designedas a shift register. The machine's controlling microprocessor placesbits of data one at a time on a transmission line, and toggles a clockline for each bit. This causes data to be sent through two shiftregister chips on each control board, each taking eight bits. There arethus 16×7 or 112 bits to be sent out. Referring to FIGS. 18A-D, the datacomes in on connector J9.1, and the clock line is J9.2. The shiftregisters used in this design are “double buffered,” which means thatthe output data will not change until there is a transition on a secondclock (R clock), which comes in on pin J9.3. The two clocks are sent toall seven boards in parallel, while the data passes through the shiftregister chips (U1 and U2) on each board and is sent on from the secondshift register's “serial out” pin SDOUT to the input pin of the nextboard in daisy chain fashion. It will be seen that a matching connector,J10, is wired in parallel with J9 with the exception of pin 1. J10 isthe “output” connector, which attaches via a short cable to J9 of thenext board in line, for a total of seven boards. The other three pins ofJ9 are used for power to run the electronics (J9.4), electronic ground(J9.5), and a common return line (J9.6) for temperature measurementfunction from the sensors.

Of the sixteen data bits sent to each board, eight control the on/offstatus of up to eight heating elements 78 directly. This can beaccomplished with a single chip because shift register U2 has internalpower transistors driving its output pins, each capable of controllinghigh power loads directly. Four of the remaining eight bits are unused.The other four bits are used to select one thermistor 87 out of themachine's total complement of forty-nine. For reasons of economy and toreduce the amount of wiring, the instrument has only oneanalog-to-digital converter for reading the forty-nine temperaturetransducers (thermistors 87), and only one wire carrying data to thatconverter. This channel must therefore be shared between all of thetransducers (thermistors 87), with the output of one of them beingselected at a time. Component U4 is an analog multiplexer which performsthis function. Of the four digital bits which are received serially, oneis used to enable U4, and the other three are used to select one of thecomponent's eight channels (of which only seven are used). If pin fouris driven low, U4 for that board 79 becomes active and places thevoltage from one of the seven channels of that board on the sharedoutput line at J9.6. Conversely, if pin four is pulled high, U4's outputremains in a high impedance state and the output line is not driven.This allows data from a selected board 79 to be read, with the remainingboards 79 having no effect on the signal. Multiplexer U4 can only beenabled on one board 79 at a time; if more than one were turned on at atime, the signals would conflict and no useful data would betransmitted.

Temperature sensing is accomplished by a voltage divider technique. Athermistor 87 and a fixed resistor (5.6 kilohms, R1-R8, contained inRS1) are placed in series across the 5 volt electronic power supply.When the thermistor is heated, its resistance drops and the voltage atthe junction point with the 5.6 kilohm resistor will drop.

There are several advantages to the design used in this embodiment.Namely, the temperature control boards 79 are small and inexpensive.Moreover, the heater boards are all identical. No “address” needs to beset for each board 79. Lastly, the service loop 90 is small in size.

An alternative potential design is that each temperature control board79 could be set up with a permanent “address” formed by adding jumperwires or traces cut on the board. The processor would send out a packetof data which would contain an address segment and a data segment, andthe data would be loaded to the board whose address matched the addresssent out. This approach takes less time to send data to a particularboard, but the address comparison takes extra hardware. It also demandsextra service loop wires to carry the data (if sent in parallel) or anextra shift register chip if the address is sent serially. As yetanother potential design is that each temperature control board 79 couldhave its own microprocessor. They could all be connected via a serialdata link to the main computer 86. This approach uses even fewerconnecting wires than the present embodiment, but the cost of hardwareis high. It also still implies an addressing scheme, meaning that theboards would not be identical. Also, code for the microprocessors wouldbe required.

EQUIVALENTS

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims. Those skilled in the artwill recognize or be able to ascertain using no more than routineexperimentation, many equivalents to the specific embodiments of theinvention described specifically herein. Such equivalents are intendedto be encompassed in the scope of the claims.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

1. A method of processing samples mounted on microscope slidescomprising: providing a plurality of slide supports on a platform, eachsupport being comprised of a heating element that underlies at least onemicroscope slide and having a surface on which the at least onemicroscope slide rests so as to transfer heat to the at least onemicroscope slide, said heating elements being capable of heating saidmicroscope slides, under independent electronic control to heat someslides to a different temperature than other slides; placing two or moremicroscope slides on the platform; providing relative motion between theplatform and a liquid dispenser; dispensing liquid from the liquiddispenser onto the slides; and on the platform, heating one slide to adifferent temperature than a second slide.
 2. A method of processingsamples mounted on microscope slides as claimed in claim 1, wherein eachslide support accommodates only one microscope slide.
 3. A method ofprocessing samples mounted on microscope slides as claimed in claim 1wherein a temperature sensor is positioned in association with a heatingelement.
 4. A method of processing samples mounted on microscope slidesas claimed in claim 1, wherein the platform is a moving platform capableof moving slides adjacent to a stationary liquid dispensing location. 5.A method of processing samples mounted on microscope slides as claimedin claim 4 further comprising: communicating data from a computer notlocated on the moving platform to electronic circuitry mounted on themoving platform; and processing the data in the electronic circuitry onthe moving platform and supplying, from the electronic circuitry on themoving platform, amounts of electrical power to the heating elementsdependent on the data, to heat one of the slides to a differenttemperature than a second one of the slides.
 6. A method of processingsamples mounted on microscope slides as claimed in claim 5, wherein eachslide support accommodates only one microscope slide.
 7. A method ofprocessing samples mounted on microscope slides as claimed in claim 4further comprising; providing a computer comprising a user interfacethrough which a desired temperature for each microscope slide isspecified, said user interface being mounted off of the moving platform;sending data from the computer to the electronic circuitry on the movingplatform over a group of conductors, the number of conductors in saidgroup of conductors being less than the number of heating elementscontrollable to individual temperatures; and processing the data in theelectronic circuitry on the moving platform, and supplying electricalpower to the heating elements from the electronic circuitry on themoving platform.